JavaScript is disabled for your browser. Some features of this site may not work without it.

Molecular analysis of genetic variation and relationships within the population of abalone (Haliotis midae) at the Sea Plant Products abalone hatchery, Hermanus, R.S.A.

Slabbert, Ruhan (2004-12)

Thesis (MSc)--University of Stellenbosch, 2004.

Thesis

ENGLISH ABSTRACT: The species Haliotis midae is the only commercially exploitable abalone
species of the six found in the South African coastal waters. This species is
under substantial pressure from both legal and illegal harvesters, to such an
extent that it could be commercially extinct within four years. Efforts to
alleviate the pressures on the natural populations of both illegal and legal
harvesting are being made. The genetic management systems for abalone
farming and ranching activities should be carefully evaluated. The loss of
genetic diversity and the risks of contaminating the gene pools of natural
populations in the vicinity of a farm should be minimized. Genetic evaluation
studies will be at great importance to acquire the necessary data needed for
genetic diversity and differentiation analysis.
The aim at this study was to develop species-specific microsatellite DNA
markers to assess the genetic diversity and differentiation within and between
the brood stock and commercial stock of the Sea Plant Products abalone farm
(Hermanus, Republic of South Africa) and natural populations related to the
brood stock. The species-specific DNA markers were also used for parentage
assignments within the tarm population (first for abalone) and preliminary OTL
(quantitative trait loci)-discovery analysis studying growth rate segregation.
Samples were taken of the farm's brood stock and commercial stock (Rows 2,
3, 4) as well as from two natural populations (Saldanha Bay and Black Rock)
related to the brood stock. Various statistical parameters and software
packages were used to assess genetic diversity and differentiation, to infer
parentage and to look for OTL's.
Eight species-specific microsatellite DNA markers were designed and used
for data analysis. Data analysis showed a loss at genetic diversity from the
brood stock to the commercial stock caused by the subdivision of the original
brood stock into rows and the differential contributions of parents to the
offspring. No genetic differentiation (Fst) was detected between the farm and natural populations, except for the offspring of Row2. levels of inbreeding
(ns) were high for all loci within the populations. Thirty-eight percent of all
studied offspring were confidently assigned to a couple. The preliminary QTldiscovery
suggested the segregation of a number of alleles and genotypes
with growth rate.
The study concluded that the commercial abalone population of the Sea Plant
Products abalone farm holds no threat to the disruption of the genetic diversity
of the natural populations. It is proposed that the farm implement a rotational
breeding program to increase the genetic diversity of the commercial
population. Any newly acquired brood stock must be profiled before their
introduction into the breeding program to assess the influence of the animals
on the current levels of genetic diversity within the farm. The accuracy and
reliability of parentage assignments and QTl-discovery need to be optimised
by adding more loci and sampling more animals or even by trying and
developing new methods.